High CPU usage after enable IOMMU


New Member
Oct 8, 2023
Ive encountered an weired behaivior with one of my VE Hosts. I need to activate the IOMMU and i followed the described steps on the PM Wiki. Right after adding "intel_iommu=on" to /etc/kernel/cmdline and updating the kernel my PM Host is constantly on 40%- 90% CPU without anything running but PCI passthrough is doing its job.
As soon as i remove the IOMMU config my host turns back to normal.

Ive now running PVE 5.15.116-1 but had this issue also with 5.15.107-2.

Does anyone have me any advice to find the cause of my problem?
And there is nothing in the system logs? And you cannot find which process is using the CPU?
Well, there is the main problem. There is no specific Service that consumes all the resources its more that every services need suddenly more power. For example even "top" peaks at 80%.
Im really not a Linux crack but the logs in /var/log seems fine.

But i just resolved the problem "by accident"...

The Server had an 4x MGig Network card installed which ive never used. So i just removed it and now everything works like a charm. Can someone maybe explain that to me?
Last edited:
Next thing I would have suggested is to look at the number interrupts thrown and compare that to running without iommu.


The Proxmox community has been around for many years and offers help and support for Proxmox VE, Proxmox Backup Server, and Proxmox Mail Gateway.
We think our community is one of the best thanks to people like you!

Get your subscription!

The Proxmox team works very hard to make sure you are running the best software and getting stable updates and security enhancements, as well as quick enterprise support. Tens of thousands of happy customers have a Proxmox subscription. Get yours easily in our online shop.

Buy now!